Crystal Structure of the Polymer Electrolyte Poly(ethylene oxide)3:LiCF3SO3

Science  05 Nov 1993:
Vol. 262, Issue 5135, pp. 883-885
DOI: 10.1126/science.262.5135.883


Ionically conducting polymers (polymer electrolytes) are under intensive investigation because they form the basis of all solid-state lithium batteries, fuel cells, and electrochromic display devices, as well as being highly novel electrolytes. Little is known about the structures of the many crystalline complexes that form between poly(ethylene oxide) and a wide range of salts. The crystal structure is reported of the archetypal polymer electrolyte poly(ethylene oxide)3:LiCF3SO3, which has been determined from powder x-ray diffraction data. The poly(ethylene oxide) (PEO) chain adopts a helical conformation parallel to the crystallographic b axis. The Li+ cation is coordinated by five oxygen atoms—three ether oxygens and one from each of two adjacent CF3SO3- groups. Each CF3SO3 in turn bridges two Li+ ions to form chains running parallel to and intertwined with the PEO chain. There are no interchain links between PEO chains, and the electrolyte can be regarded as an infinite columnar coordination complex.